It certainly does look like a vintage thuringian/escher! You're lapping seemed to confirm the feel of it, as it does lap easily (as least the ones I have) and leaves a slurry. But I agree with pjrage that it does have a different feel that my coticules, but that may just be your personal interpretation.

Try it on an already shave-ready edge for a few laps, strop it and try shaving with it! If you have a microscope it wouldn't hurt to look at the edge under magnification to see how it's affected the scratch pattern.

But seriously, $1???? I'm not jealous...